2. What airline was the launch customer for the MD-83?

Good job, Wally. I knew you'd come up with it sooner than later! ^

7. Which airport of a major U.S. city was originally named for a man who had died in an airplane crash on the land upon which that airport is built?

Somehow I missed noticing question 7 -- of course it's here in New Orleans -- MSY -- Moisant Stock Yards, named after John Moisant, who crashed in 1910 in the area that became MSY. Interestingly he designed, built and flew the first metal (aluminum) airplane in 1909.

Right on, miniliq! What took you so long?

12. This airline offered the only nonstop between Houston and Cincinnati?

My 4/82 OAG showed a DL nonstop, and my 6/79 shows AA, so I correct my earlier answer to try AA.

Alas, your OAG is one year too late for this question which is based upon the 1981 schedules. So - we know it wasn't AA or DL... What other airline could it possibly be...?

13. These two airlines provided the only nonstop flights between Milwaukee and Kansas City (in 1981)

I'll try Braniff and United.

United is correct, but not Braniff. The answer is a bit surprising but here's a hint - the equipment used by this other airline was not manufactured by Boeing.